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Fuel pump and inertia switch not getting power?

Tiny
HITO_300
  • MEMBER
  • 1988 FORD F-150
  • 5.0L
  • V8
  • 4WD
  • MANUAL
  • 160,000 MILES
What can be the cause of no power to inline fuel pump and no power to inertia switch? Checked for power on relays and they have power so do all fuses replaced the fuel pump relay and still nothing. The truck cranks but won't fire I put power to the inline fuel pump and it started working but when not doing that there's no power to pump.
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Monday, September 16th, 2024 AT 7:57 PM

12 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Before we jump directly into the fuel system, have you checked to see if there is spark at the plugs? I ask because if the EEC relay fails, it will shut down both fuel and ignition spark.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

I can't find a pic of the relay, but it's located on the air cleaner support bracket, under a plastic cover/shield.

Do me a favor. Switch that relay with a different one having the same part number and see if it works.

Let me know.

See pic below.
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Monday, September 16th, 2024 AT 8:32 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Before we jump directly into the fuel system, have you checked to see if there is spark at the plugs? I ask because if the EEC relay fails, it will shut down both fuel and ignition spark.

I can't find a pic of it, but it's located on the air cleaner support bracket, under a plastic cover/shield.

Do me a favor. Switch that relay with a different one having the same part number and see if it works.

Let me know.

See pic below.
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Monday, September 16th, 2024 AT 8:32 PM
Tiny
HITO_300
  • MEMBER
  • 6 POSTS
I'm pretty sure we have spark because we sprayed ether in it and it tried to fire.
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Tuesday, September 17th, 2024 AT 10:51 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Okay, we need to return to the inertia switch. Are you certain there is no power at the brown wire to it? Are you testing it with a test light or multimeter? Are you using a known good ground location when testing?

If that is all good, try switching the EEC relay. The relay is what powers the electronic engine control module. If the relay doesn't make a change, we need to access the EEC module under the dash and check pin 8 for damage, corrosion, or any evidence of failure. See pics below

Let me know.

Joe

See pics below.
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Tuesday, September 17th, 2024 AT 7:42 PM
Tiny
HITO_300
  • MEMBER
  • 6 POSTS
Hi, here's an update: I rewired the inertia switch from the relay turns out it lost power somewhere down the wire so my fuel pump comes on and inertia switch work now but I think it has a fuel problem I replaced the fuel filter and as I previously said I replaced the fuel pump in the tank only think I can think of is maybe the inline fuel pump is weak and can’t provide enough fuel pressure.
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Tuesday, September 17th, 2024 AT 9:17 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Were you able to check the pressure being supplied? I attached the specifications for pressure below.

Let me know.

Joe
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Wednesday, September 18th, 2024 AT 5:42 PM
Tiny
HITO_300
  • MEMBER
  • 6 POSTS
I haven't checked the pressure. I replaced the in-line fuel pump today but the o ring on my reservoir fuel filter is gone so it just dumps gas when you turn the ignition. Do you know what the part number is for that or where to get one?
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Wednesday, September 18th, 2024 AT 6:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

The only thing I have for that is the fuel filter part number. It's E7DZ9155A. If you are looking for the quick connectors, I don't have the OEM part numbers. You would likely have to find something at a parts store.

Let me know.

Joe
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Wednesday, September 18th, 2024 AT 7:41 PM
Tiny
HITO_300
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  • 6 POSTS
It's not the normal fuel filter it's like the selector but I only have one tank I added a picture so you can see it.
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Thursday, September 19th, 2024 AT 4:56 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Do you mean it is similar, but your truck only has one tank from the factory? I'm not sure I understand.

Let me know.

Joe
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Thursday, September 19th, 2024 AT 6:27 PM
Tiny
HITO_300
  • MEMBER
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Okay, I got that problem fixed the truck still won't start just cranks it has nee fuel pumps and filters I haven't check the pressure yet, but do you have any idea on what it can be.
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Friday, September 20th, 2024 AT 4:18 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

If it tried starting with starting fluid, we know it isn't getting fuel. So, if the pump is new the next thing I would check is if there is power to the fuel injectors.

If you look below, I attached the schematic for the injectors. Note that each one has a red wire. With the key in the run position, the red wires should have power.

Check to see if that is the case and let me know.

Take care,

Joe

See pic below.
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Friday, September 20th, 2024 AT 8:02 PM

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